1. Field of the Invention
The present invention relates to a method for searching trunks in an exchange system. The exchange system has a distributed control structure for distributively accommodating the trunks to several subsystems which control routing to trunks. In this exchange system, the present invention particularly relates to a method for searching trunks that a subsystem searches a standby idle trunk for preparing a next trunk usage, stores information of the standby idle trunk and then processes a current call service by connecting the preset trunk when the call is required, whereby minimizing load of the system as well as improving a search speed of the trunk.
2. Background of the Related Art
Interoffice trunk line connection among telecommunications N/Ws composed of a plurality of exchanges systems, is carried out in a switching subsystem for controlling a respective trunk. The switching subsystem connects a call to trunks which are selected by whether the respective trunk may serve or not according to the trunk state, such as failure or call service state. And the switching subsystem is established by a trunk distributed control structure, which divides calls in each trunk group and allocates calls to each trunk group.
There is now described about a usual trunk allocating method. In order to set a speech path from an originating exchange to a terminating exchange, a corresponding switching subsystem searches each trunk state in its trunk group when requiring a trunk allocation to a plurality of switching subsystems in the terminating exchange. In case that there is no idle trunk in the corresponding trunk group, the corresponding switching subsystem moves a call service into another switching subsystem in the same trunk group. The another switching subsystem processes searching state of each trunk about a corresponding trunk group, repeatedly.
In other words, the switching subsystem receiving request of the trunk allocation in the exchange system, searches each trunk state of its trunk group and processes a call service through a corresponding idle trunk in case that there is the idle trunk, i.e. a trunk which is able to serve.
However, there are possibilities to have severe problems, for example interruption of overall services in a corresponding exchange system because system load raises continuously as busy hour call attempts (BHCA) in the corresponding exchange system, increased referring to FIG. 1.
Because of searching all trunks repeatedly regardless of each trunk state in a corresponding trunk group whenever a call is generated, it causes a call process to be delayed. In addition, it may raise load during processing the call by searching the trunk state unnecessarily in case that there is no idle trunk in a corresponding trunk group in the conventional trunk allocating method.
Accordingly, in order to solve the problems in the prior art, it is an object of the present invention to provide a trunk search method by searching an idle trunk in a corresponding trunk group in an exchange system, setting the searched information, and then connecting the preset idle trunk as soon as a call is required, resulting in processing a call service quickly.
In one embodiment of the present invention to achieve the object, a method for searching trunks by a plurality of switching subsystems in an exchange system having a distributed control structure for distributing the trunks to the switching subsystems, the method comprising searching a first idle trunk for a required call service in a corresponding trunk group, searching a second idle trunk in the trunk group, setting the second idle trunk as an idle trunk standby information (SCHP; SearCH Pointer value) for preparing a next call service, and storing the information.
In another embodiment of the present invention to achieve the object, a method for searching trunks by a plurality of switching subsystems in an exchange system having a distributed control structure for distributing the trunks to the switching subsystems, the method comprising allocating the trunk by searching an idle trunk in a corresponding trunk group in accordance with a trunk allocation request and then setting an idle trunk information for a current call service, and allocating a standby trunk by searching another idle trunk in the trunk group in accordance with the trunk allocation request and then setting an idle trunk standby information (SCHP value) for a next call service.
In the other embodiment of the present invention to achieve the object, a method for searching trunks by a plurality of switching subsystems in an exchange system having a distributed control structure for distributing the trunks to the switching subsystems, the method comprising searching whether there is an idle trunk in a trunk group in accordance with a trunk allocation request, setting the searched idle trunk as an idle trunk information for a current call service in case that there is the idle trunk in the corresponding trunk group, searching whether there is another idle trunk in the trunk group, setting another searched idle trunk as an idle trunk standby information for a next call service in case that there is another idle trunk in the trunk group, and processing the current call service by using the idle trunk set in the idle trunk information.